further extended through well-designed SERS substrates. [5,6] Although many kinds of SERS substrates have been reported, extensive studies have mainly focused on enhancing the sensitivity by generating more SERS-active sites (commonly known as "hot spots") on the substrates using strategies such as colloidal assembly, lithography technique, and nanoimprinting. [7][8][9][10][11] Besides, the wetting properties of the SERS substrates have recently gained much attention. Typically, the SERS substrates that are covered with noble metals are naturally hydrophilic, which in turn restricts further applications such as trace analysis or single-molecule detection because of the low probability in locating the analyte molecules at SERS-active sites especially for highly diluted solutions. [12,13] To overcome the limitations, many strategies have been reported. For example, Yang et al. developed a method by aggregating target molecules and metal nanoparticles into small regions. [14] A slippery liquid-infused porous surface consisting of a Teflon membrane and a perfluorinated lubricant, which eliminates the adhesion of the droplets, was used. Such a surface was found to lead to a constant water contact angle (WCA) during the solvent evaporation process and enhance the aggregation efficiency of the gold nanoparticles (AuNPs) and the target molecules. In another example, Chen et al. demonstrated a strategy to achieve effective aggregation by applying the coffee ring effect using cellulose nanofibers (CNFs) and AuNPs. [15] Suspended analyte particles were carried and accumulated at the drop edges by the hydrodynamic flow, and eventually, formed ring-shape SERS sensitive regions. The CNF-AuNPs substrates were found to have a wider SERS detection zone (L D ≥ 300 µm) compared with the conventional method (L D ≤ 30 µm), which can be attributed to the unique surface properties. Park et al. also developed a facile protocol by placing the analyte molecules at the SERS-active nanogaps of the nanopillars to achieve high sensitivity. [16] By controlling the surface energy of plasmonic nanopillars through the selective removal process, a wide range of WCA from 165.8° (superhydrophobic surface) to 40.0° (hydrophilic surface) was obtained. Under the optimized wetting conditions, successful detection Surface properties are essential for substrates exhibiting high sensitivity in surface-enhanced Raman scattering (SERS) applications. In this work, novel SERS hybrid substrates using polystyrene-block-poly(methyl methacrylate) and anodic aluminum oxide templates is presented. The hybrid substrates not only possess hierarchical porous nanostructures but also exhibit superhydrophilic surface properties with the water contact angle ≈0°. Such surfaces play an important role in providing uniform enhanced intensities over large areas (relative standard deviation ≈10%); moreover, these substrates are found to be highly sensitive (limit of detection ≈10 −12 m for rhodamine 6G (R6G)). The results show that the hybrid SERS substrates can achieve the simu...

Poly(ionic liquid)s (PILs) have attracted great attention because they preserve conventional characteristics of polymers while having special features of ionic liquids, such as good ionic conductivity and excellent electrochemical and thermal stability. The solvent absorption behaviors and solvent-induced responsiveness of PIL elastomers, however, have been less investigated. In this work, we prepare two PILs, poly[C3mim-MA][Br] and poly[C3mim-MA]-[TFSI], and examine their surface hydrophilicities and solvent-induced responsiveness. Ionic liquid monomers are synthesized and then polymerized with initiators and cross-linkers via free radical polymerization, forming PIL elastomers. The anions in the monomers can be replaced using an ion exchange process to prepare PIL elastomers with different anions. The surface properties, swelling behaviors, and solvent responsiveness of the PIL elastomer films with different anions and cross-linker ratios are investigated. The surface hydrophilicities of the PIL films are characterized by water contact angle measurements; the poly[C3mim-MA][Br] elastomer films are more hydrophilic than the poly[C3mim-MA][TFSI] elastomer films. Due to the different hydrophilicities, the poly[C3mim-MA][Br] and poly[C3mim-MA][TFSI] elastomer films can be swollen selectively in water and acetone, respectively. For both elastomers, the swelling degrees are higher at lower cross-linking densities, and the volume expansions can be up to 655%. Furthermore, we investigate the solvent-vapor-induced responsiveness of bilayer films of PIL elastomers and polyimide (PI) tapes. The bilayer films can be bent selectively by exposing them to water or acetone vapors, depending on the anions.